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1. Field of the Invention
The present invention relates, generally, to power supply apparatus and methods. More particularly, the invention relates to an extended range variable power supply. The invention has particular utility in pulse plating power supplies.
2. Background Information
The deposition of metal on a substrate using direct current is a well-known technology used in a number of metal finishing industries, especially the electronics industry. A recent advance in this technology is the pulsing of direct current during the plating process. This innovation provides a series of pulses of direct current (D.C.), of equal amplitude and duration in the same direction, or alternating directions, separated by periods of zero current. The pulse rate (frequency) and ON and OFF times (duty cycle) are controllable to meet the requirements of a given application. The pulses are routinely employed at a rate of 500 to 10,000 times per second. This plating method favors the initiation of grain nuclei and significantly increases the number of grains per unit area. The resulting metal coating is a finer grain deposit with better characteristics and properties than conventionally plated coatings. The pulse plating technology has become a requirement in the electronics industry where the process and/or product specification are highly restrictive and sophisticated.
In addition to the composition of the liquid phase containing soluble metal salts, which are the source of the deposited metal(s), a critical component of the system is the regulated power supply that delivers pulsed current to the substrate. Many power supply devices and methods for their operation are know, but are believed to have significant limitations and shortcomings. The performance of pulse and pulse reversing power supplies presently used for electroplating is limited by the requirement to satisfy a wide spectrum of load conditions while maintaining output stability. This requirement limits the operational range in which these power supplies deliver optimal performance in current or voltage regulation modes. The optimal operating range for these devices is from about 5% to about 100% of the peak rated current output capability of the power supply. For this and other reasons, a need exists for the present invention.
The invention provides an extended range power supply, which is believed to fulfill the need and to constitute an improvement over the background technology.
All US patents and patent applications, and all other published documents mentioned anywhere in this application are incorporated by reference in their entirety.
The present invention provides an extended range power supply system. In one embodiment, the apparatus includes a power source for providing operational power with a power supply circuit connecting with the power source for regulating the operational power. A current sensing circuit is connected with the power supply circuit, the current sensing circuit including a plurality of current sensing elements, each sensing element configured for a selected output range, with each sensing element individually operatively activated, and each sensing element providing a feedback signal. The current sensing circuit is connected with, and supplies current to, a load. A control loop compensation circuit is connected with the current sensing circuit for receiving the feedback signal and with the power supply circuit to provide an error signal. The control loop compensation circuit includes a like plurality of control loop compensation components, each operatively associated with one current sensing element for receiving a feedback signal. Activation of one current sensing element and an associated control loop compensation component for a desired output current range provides for optimum performance of the power supply at the selected peak output current range.
Significant features of the invention include optimal performance through an output range of 0.1% to 100% of peak rated output current for a pulse/pulse reversing power supply system.
The features, benefits and objects of this invention will become clear to those skilled in the art by reference to the following description, claims, and schematic drawings.